fix PEP8 E303 and make the code check more strict

.github/workflows/test_code.yml

@@ -2,7 +2,7 @@ name: test-code
 on: [push, pull_request]
 jobs:
   lint-python-code:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v1
       - uses: ricardochaves/python-lint@v1.4.0
@@ -14,4 +14,4 @@ jobs:
           use-black: false
           use-mypy: false
           use-isort: false
-          extra-pycodestyle-options: "--ignore=E226,E301,E302,E303,E402,W503,W504 --max-line-length=120 --max-doc-length=120"
+          extra-pycodestyle-options: "--ignore=E402,W503,W504 --max-line-length=120 --max-doc-length=120"